JP3307049B2 - Discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for supplying a high-frequency current to a discharge lamp by a high-frequency switching operation.

[0002]

2. Description of the Prior Art FIG. 1 is a circuit diagram of a conventional discharge lamp lighting device, and FIG. This conventional example is a full bridge discharge lamp lighting device. Its main circuit configuration is parallel to a power supply circuit composed of an AC power supply E and a rectifier circuit D, and connected in series with a series connection circuit of switching elements S ₁ and S _2. a series connection circuit of elements S _3, S _4, between the switching element S _1, S ₂ of the connection point a and the switching element S _3, the connection points of S ₄ B, series inductor L and the discharge lamp 2 A capacitor C for preheating is connected between the filaments of the discharge lamp 2. The switching elements connected in series do not turn on at the same time, but form a full bridge circuit that alternately turns on and off the switching elements connected in series so that the on-time and the off-time are the same. Each switching element S _{1 to} S ₄
It is controlled by a control signal V ₁ ~V ₄ shown in FIG. 2 (a) ~ (d) supplied from the control circuit 1.

Hereinafter, a specific circuit operation will be described. Times of Day
t₀, The control signal V₁And V_FourIs low level
Switching element S₁And S_FourTurns off and the control signal V
_TwoAnd V _ThreeBecomes high level, and the switching element S_TwoWhen
S_ThreeTurns on, the load current Iz flowing through the inductor L
At time t due to resonance₀Because it is continuous with the previous current,
Flow from A to B as shown in 2 (e), and then from B
It flows in the direction of A. Time t₁, The control signal V₁When
V_FourBecomes high level, and the switching element S₁And S_Four
Turns on and the control signal V_TwoAnd V_ThreeGoes low,
Switching element S _TwoAnd S_ThreeTurns off, the load current Iz
At time t due to resonance₁Because it becomes continuous with the previous current, B
Flows from A to B, and then flows from A to B.
Time t_TwoAt time t₀Control signal V₁
And V_FourBecomes low level, and the switching element S₁And S
_FourTurns off and the control signal V_TwoAnd V_ThreeBecomes high level,
Switching element S_TwoAnd S_ThreeTurns on. These series
A high-frequency current can be supplied to the discharge lamp 2 by operation.
You.

[0004] In this conventional example, for example, the load impedance is suddenly changed by the discharge lamp end of life, etc., in the case of increasing the load current Iz flowing through the inductor L, as shown at time t ₃ is gradually increased. Then, at time t ₄ ,
If the abnormal current is detected, the control signal V ₁ at time t ₅
By increasing the frequency of ~V _4, it has limited the increase in the load current Iz by increasing the operating frequency of the switching element. However, this prior art, always the load circuit is connected to the power supply, as shown at time t _6, the load current Iz is changed abruptly, there is a problem that the stress of the switching element is increased . Further, since the waveform is distorted at time t ₆ before there is a problem that noise increases.

[0005]

As described above, in the conventional discharge lamp lighting device, when the load impedance suddenly changes and increases due to the end of the life of the discharge lamp or the like, the operating frequency of the switching element is increased to increase the load current. However, since the load circuit is always connected to the power supply, the load current changes sharply, the stress on the switching elements increases, and the waveform is distorted, resulting in a large noise. There was a problem of becoming.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a discharge lamp lighting device for controlling a load current of a discharge lamp by controlling a switching element, in which a sudden change in load impedance is caused. In some cases, a sudden change in the load current is prevented to reduce the stress on the switching element, and also suppress the waveform distortion to reduce noise.

[0007]

In order to solve the above-mentioned problems, a discharge lamp lighting device according to the present invention is shown in FIG.
So that they are connected in parallel to the DC power
The first switching element S ₁ that performs on / off operation and the second switching element S ₁
A first series circuit of the switching element S _2, a DC power source
Are connected in parallel and turn on and off without turning on at the same time
Third switching element S ₃ and fourth switching element
A second series circuit of a S _4, the first and second series times
Connected between the connection points A and B of the switching element on the road.
At least a series resonance circuit of inductor L and capacitor C
And a load circuit comprising a discharge lamp 2 and the first series circuit
High-voltage side switching element S ₁ and the second series circuit
The same switching and the switching element S ₄ of the low-pressure side
ON / OFF operation at the same time in a cycle, and the low state of the first series circuit
Of the switching element S _{2 on the} compression side and the second series circuit.
Substantially the same switching frequency and the switching element S ₃ of pressure side
Control circuit to perform on-off operation almost simultaneously in the period
1. The discharge lamp lighting device according to
Is the on / off state of the switching element
Timing that turns off and on almost simultaneously
In the range from the same phase, which is
First control means for continuously changing, and changing the operating frequency
And second control means for causing
The first control means is given priority over the second control means and the load
In the event of an abnormality that controls the current supplied to the circuit in a direction that limits it
It is characterized by having a protection means .

[0008]

According to the present invention, the operation of the switching element is
Priority to the change of the operating frequency, one of the switches connected in series.
Switching in series with the other
The load circuit is connected to the power supply circuit by changing the operation phase of the element.
Attenuates load current by reducing duration
With the above operation, even if the load impedance suddenly changes and increases at the end of the life of the discharge lamp, etc., even if the load impedance increases, it prevents the load current from changing sharply,
The stress of the switching element can be reduced. Further, it is possible to suppress an increase in load current while suppressing waveform distortion and reducing noise.

[0009]

FIG. 3 is an operation waveform diagram of one embodiment of the present invention. The circuit diagram of the present embodiment is the same as the conventional example of FIG. According to the present embodiment, the on / off timing of one switching element connected in series with respect to the switching element connected in series is continuously changed within the range of 180 degrees from the same phase. It is something that changes it.
Each switching element is controlled by a control circuit as shown in FIGS.
(D) is controlled by a control signal V ₁ ~V ₄ shown.

Hereinafter, a specific circuit operation of this embodiment will be described.
Will be explained. Time t in FIG.₀, The control signal V₁When
V_FourBecomes high level, and the switching element S₁And S_Four
Turns on and the control signal V_TwoAnd V_ThreeGoes low,
Switching element S_TwoAnd S_ThreeTurns off, the inductor L
The load current Iz flowing through₀Previous current
Flow from B to A, and eventually A
A current flows in the direction of the arrow B. Load flowing through inductor L
The current Iz flows as shown in FIG. 3 time
t₁, The control signal V₁And V_FourIs low level
Switching element S₁And S_FourTurns off and the control signal V
_TwoAnd V_ThreeBecomes high level, and the switching element S_TwoWhen
S_ThreeIs turned on, the load current Iz changes at time t due to resonance.₁
Since it is continuous with the previous current, it flows from A to B,
Eventually, it flows from B to A. Time t_TwoAt the time
Time t₀Similarly, the control signal V₁And V_FourIs high level
And the switching element S₁And S_FourTurns on and the control signal
Issue V_TwoAnd V_ThreeBecomes low level, and the switching element S
_TwoAnd S_ThreeTurns off. Next, for example, the end of discharge lamp life
When the load impedance changes suddenly and increases,
Time t_Three, The load current Iz flowing through the inductor L
Increases at time t_FourThe current anomaly that increases with
If detected, time t_Five, The control signal V₁But
-Level, control signal V_TwoBecomes high level and the control signal
V_ThreeAnd V_FourConnect the power supply circuit and the load circuit without changing
Make no period. And time t₆Control signal V₁And V
_FourAnd V _TwoAnd V_ThreeIs the phase difference set in advance.
θ, the control signal V_ThreeIs high level and the control signal V_Four
Becomes low level, and the power supply circuit and load circuit are connected.
You. Here, the control signal V₁And V_FourAnd control signal V_TwoAnd V
_ThreeControl signal V for the maximum period during which₁
And V_FourAnd control signal V_TwoAnd V_ThreeActually turn on at the same time
Assuming that the period ratio is the “overlap ratio”, the control signal V_TwoAnd V
_ThreeUntil it reaches the set overlap rate.
Keep state. And time t₇, The control signal V_ThreeWhen
V_FourWithout changing the control signal V₁Is high level, control
Signal V_TwoBecomes low level, and the power supply circuit and load circuit again
Make a period to connect.

Time t₈, The control signal V_TwoAnd V_Threeof
When the phase difference reaches the preset phase difference θ, the control signal
Issue V_ThreeIs low level and the control signal V_FourIs high level
Thus, the power supply circuit and the load circuit are connected. Time t₉smell
And time t_FiveThe state is similar to
, The load current Iz gradually decreases.
Go a little. And after a certain amount of time,
Time t_Ten, The control signal V₁And V_TwoChange the operating frequency of
To Control signal V₁Becomes high level and the switch
Element S₁Turns on and the control signal V_TwoIs low level
Switching element S_TwoTurns off and the control signal V_ThreeHa
And the switching element S_ThreeKeeps on
Control signal V_FourKeeps low level and switches
Element S_FourThe load circuit is connected to the power supply circuit because
Although the load current Iz flowing through the inductor L is not
Time t_TenBecause it becomes continuous with the previous current,
It flows as shown in (e). Next, at time t₁₁At the time
t_FiveFrom time t₉Control signal so that the overlap rate is the same as
Issue V_ThreeBecomes low level, and the switching element S_ThreeBut
Control signal V_FourBecomes high level and switching
Element S_FourIs turned on, the load circuit is connected to the power supply circuit.
The load current Iz flowing through the inductor L is
It flows like 3 (e). Then, at time t₁₁~ T₁₄In
At time t_Five~ T ₉And operating frequency is different, but similar
Perform the operation. A series of these operations allows the load impedance to be
When the dance changes suddenly, the load circuit
Shorten the connection time, and
By increasing the frequency, it flows to the inductor L
Limiting the increase in the load current Iz,
Noise and waveform distortion as well as noise.
To reduce. The load current Iz flowing through the inductor L
Is sufficiently small, the overlap rate is maximized and the weak current
Mode.

FIG. 4 shows a transition of a series of states of these circuits. In FIG. 4, the horizontal axis indicates the operating frequency f, and the vertical axis indicates the overlap rate. In the figure, state A is a lamp startable area, state B is a lamp preheatable area, and state C is a no-load area. The area on the left side of the one-dot chain line is the lightable area. As is clear from FIG. 4, when the load current changes abruptly, the operating frequency f is increased while keeping the overlap ratio small and kept constant. When the load current is sufficiently small, the overlap ratio is maximized. This embodiment is a feature of the present embodiment in that the circuit is set to a weak oscillation mode.

FIG. 5 is a diagram illustrating the operation of the second embodiment of the present invention.
FIG. The main circuit configuration of this embodiment is the same as that of the conventional example of FIG.
And each switching element S₁~ S_FourIs the control circuit
The control signal V shown in FIGS.₁
~ V_FourIs controlled by Below, the specific circuit operation
explain about. To reduce the load current Iz during dimming
At time t in FIG.₀, The control signal V₁Is high level
And the switching element S₁Turns on and the control signal V
_TwoBecomes low level, and the switching element S_TwoIs off
And the control signal V_ThreeKeeps high level and switches
Element S_ThreeKeeps on and the control signal V_FourStays low level
Holding, switching element S_FourKeeps off, so the load
The circuit is not connected to the power supply circuit, but the load current Iz
Time t₀Because it becomes continuous with the previous current,
It flows as shown in (e). Time t in FIG.₁In, control
Signal V_ThreeBecomes low level, and the switching element S_ThreeBut
Off and control signal V_FourBecomes high level and switches
Element S_FourTurns on and the control signal V ₁Keeps high level
And the switching element S₁Keeps on and the control signal V_Two
Maintains the low level, and the switching element S_TwoIs off
The load circuit is connected to the power supply circuit and the current is
Due to the shaking, it flows as shown in FIG. Next, the time shown in FIG.
t_Two, The control signal V₁Becomes low level and the switch
Switching element S₁Turns off and the control signal V_TwoIs high level
And the switching element S_TwoTurns on and the control signal V_Three
Maintains the low level, and the switching element S_ThreeIs off
Then, the control signal V_FourMaintains a high level and switches
Element S_FourThe load circuit is connected to the power circuit
Although not connected, the load current Iz_TwoLess than
Since the current is continuous with the previous current, the current flows as shown in FIG.
You. Time t in FIG._Three, The control signal V_ThreeIs high level
And the switching element S_ThreeTurns on and the control signal V
_FourBecomes low level, and the switching element S_FourTurns off
Then, the load circuit is connected to the power supply circuit, and the load current Iz is
Due to the resonance, it flows as shown in FIG. And in FIG.
Time t_FourAt time t₀Is the same as
repeat.

Next, for example, at time t in FIG._FiveWith discharge lamp life
Load impedance changes suddenly at the end of life and increases
In this case, the load current Iz flowing through the inductor L increases,
Time t in FIG.₆, Increasing load current anomalies
Is detected, the time t in FIG. ₇, The control signal V₁
Becomes low level, and the switching element S₁Turns off,
Control signal V_TwoBecomes high level, and the switching element S
_TwoTurns on and the control signal V_ThreeMaintains a low level and switches
Switching element S_ThreeKeeps turning off, and the control signal V_FourIs Haile
The bell is maintained and the switching element S_FourKeeps on
Is the control signal V₁And V_FourAnd V_TwoAnd V_ThreePhase difference
Increase the phase difference θ to the set value,
The time during which the circuit is connected is shortened and the time t₈In, control
Signal V₁Maintains the low level, and the control signal V_TwoIs high leve
Control signal V_ThreeBecomes high level and the control signal
V_FourBecomes low level at time t_ThreeIs the same operation as
You.

Then, at time t₈~ T₁₂Indicates that the overlap rate is
Time t₀~ T_FourBy repeating the same operation as
To reduce the connection time between the power supply circuit and the load circuit.
The load current Iz is further reduced. And to some extent
After a lapse of time, time t₁₃, The control signal V₁~ V
_FourChange the operating frequency of Control signal V₁But Lorebe
Control signal V_TwoBecomes high level and the switching element
Child S_TwoTurns on and the control signal V_ThreeMaintains a low level,
Switching element S_ThreeKeeps turning off, and the control signal V _FourHa
And the switching element S_FourKeeps on
Therefore, the load circuit is not connected to the power supply
Flow Iz is caused by resonance at time t₁₃It becomes continuous with the previous current
Therefore, it flows as shown in FIG. Next, at time t₁₄smell
And time t ₈From time t₁₂So that the overlap rate is the same as
And the control signal V_ThreeBecomes high level and the switching element
Child S_ThreeTurns on and the control signal V_FourGoes low,
Switching element S_FourIs turned on, the load circuit
And the load current Iz is caused by resonance, as shown in FIG.
Flows like Then, at time t₁₄~ T₁₇Is the time t₈~ T
₁₂Although the operation frequency is different, the same operation is performed. These series
Operation, the load current changes sharply in this circuit.
When the load is set to a value smaller than the
Reduces the time the circuit is connected to the power supply and reduces
Is increased, and then the control signal V₁~
V_FourBy changing the switching frequency of
Limit the increase in the load current Iz. This allows the switchon
The stress of the switching element and the waveform distortion
Noise can be reduced. And enough
As the load current decreases, the circuit will be
Set to the weak oscillation mode.

FIG. 6 shows a transition of a series of states of these circuits. 6, the horizontal axis represents the operating frequency f, and the vertical axis represents the overlap ratio. In the figure, state A is a lamp startable area, state B is a lamp preheatable area, and state C is a no-load area. The area on the left side of the one-dot chain line is the lightable area. As is clear from FIG. 6, when the load current changes abruptly, the operating frequency is increased while keeping the overlap ratio constant at a value smaller than the overlap ratio at the time of dimming, and the load current is sufficiently reduced. In this case, the feature of the present embodiment is that the overlap ratio is maximized and the circuit is set to the weak oscillation mode.

FIG. 7 is a diagram for explaining the operation of the third embodiment of the present invention. The main circuit configuration of the present embodiment is the same as that of the conventional example of FIG. 1, and each of the switching elements S _{1 to} S ₄ is controlled by a control signal V ₁ shown in FIGS. 7A to 7D supplied from a control circuit.
It is controlled by ~V _4. Hereinafter, a specific circuit operation will be described. During dimming, in order to reduce the load current, similarly to the operation of changing the overlapping ratio described in the second embodiment, also in this embodiment to repeat the same operation as the time t ₀ ~t _4. Then, for example, the load impedance is suddenly changed by the discharge lamp end of life, such as at time t _5, when increasing the load current is gradually increased, when detecting the abnormality of the load current to continue to increase at time t _6, at time t _7, the control signal V ₁ is set to the low level, and the switching element S ₁ is turned off, the control signal V ₂ becomes high level,
The switching element S ₂ is turned on, the control signal V ₃ maintains a low level, the switching element S ₃ continues to be turned off, the control signal V ₄ maintains a high level, and the switching element S 3
Since ₄ continues to turn on, but the load circuit is not connected to the power supply circuit and the load current for a continuous and time t ₇ the previous current by resonance, it flows as shown in FIG. 7 (e). At this time,
Changing the control signals V ₁ and V _2. Then, at time t _8, control signals V ₁ and V ₄ and V ₂ and V ₃ the time t ₀ ~
To the same overlap rate and t _4, the control signal becomes high level, the switching element S ₃ is turned on, the control signal V
₄ becomes low level, the switching element S ₄ is turned off, the load circuit is connected to the power supply circuit, a load current flows as shown in FIG. 7 (e) by the resonance. Then, at time t ₉
t ₁₃ is time t ₀ ~t ₄ and the operating frequency is changed, the overlap ratio is performed the same operation at a constant, these series of operations, when the load current changes abruptly, the load circuit power supply circuit The connection time is reduced, the increase in the load current is limited, and the stress on the switching element is reduced. Then, when the load current becomes sufficiently small, the overlap ratio is maximized to set the weak current mode.

FIG. 8 shows a transition of a series of states of these circuits. 8, the horizontal axis represents the operating frequency f, and the vertical axis represents the overlap ratio. In the figure, state A is a lamp startable area, state B is a lamp preheatable area, and state C is a no-load area. The area on the left side of the one-dot chain line is the lightable area. As is clear from FIG. 8, a feature of the present embodiment is that the operating frequency is increased while the overlap ratio is kept constant.

FIG. 9 is a diagram for explaining the operation of the fourth embodiment of the present invention. The main circuit configuration of the present embodiment is the same as that of the conventional example of FIG. 1, and each of the switching elements S _{1 to} S ₄ is provided with a control signal V ₁ shown in FIGS. 9A to 9D supplied from the control circuit.
It is controlled by ~V _4. Hereinafter, a specific circuit operation will be described. During dimming, in order to reduce the load current, similarly to the operation of changing the overlapping ratio described in the second embodiment, also in this embodiment, repeatedly perform the same operation at time t ₀ ~t _4. Then, for example, the load impedance is suddenly changed by the discharge lamp end of life, such as at time t _5, when increasing the load current is gradually increased, when detecting the abnormality of the load current to continue to increase at time t _6, control signal V ₁ is set to the low level at time t _7, the switching element S ₁
Turns off, the control signal V ₂ goes high, the switching element S ₂ turns on, the control signal V ₃ maintains the low level, the switching element S ₃ continues to turn off, and the control signal V 2
₄ keeps the high level and the switching element S ₄ keeps on, so the load circuit is not connected to the power supply circuit,
Because load current becomes continuous with the time t ₇ the previous current by resonance, it flows as in FIG. 9 (e). At this time, the control signals V ₁ and V ₂ are changed. Then, at time t _8, control signals V ₁ and V ₄ and V ₂ and V ₃ in order to reduce the overlap ratio from time t ₀ ~t ₄ a, control signal V ₁ and V ₄ and V ₂ and V ₃ Is increased to a previously set phase difference θ, the overlap ratio is reduced, the control signal V ₃ goes high, the switching element S ₃ turns on, and the control signal V ₄ goes low. , the switching element S ₄ is turned off, the load circuit is connected to the power supply circuit, a load current Iz
Flows due to resonance as shown in FIG. Thereafter, at times t _{9 to} t _13, although the frequency and the overlap rate are different from those of the times t _{0 to} t ₄ , the same operation is performed, and by a series of these operations, the overlap ratio with the control signal is increased from a certain set time. By simultaneously changing each of them, the time during which the load circuit is connected to the power supply circuit decreases when the load current changes sharply. As a result, the increase in the load current Iz is limited, and the stress on the switching element can be reduced. Also,
Waveform distortion is reduced, and noise can be reduced. Then, when the load current Iz becomes sufficiently small, the overlap ratio is maximized to set the weak oscillation mode.

FIG. 10 shows a series of state transitions of these circuits. In FIG. 10, the horizontal axis indicates the operating frequency f, and the vertical axis indicates the overlap rate. In the figure, state A is a lamp startable area, state B is a lamp preheatable area, and state C is a no-load area. The area on the left side of the one-dot chain line is the lightable area. As is apparent from FIG. 10, the feature of the present embodiment is that the operating frequency is increased while the overlap ratio is reduced.

Next, FIG. 11 is a diagram for explaining the operation of the fifth embodiment of the present invention, showing the transition of the state of the circuit operation. The main circuit configuration of the present embodiment is the same as that of the conventional example of FIG. From the state A operating in the lamp startable area, the load impedance suddenly changes due to the end of the life of the discharge lamp, the load current increases, and when an abnormality is detected, the control signals V _{1 to} V ₄ up to the state C in the no-load area. , The overlap rate is reduced, and the time during which the power supply circuit is connected to the load circuit is reduced to limit the increase in load current. Then, when limits to some extent the load current, as with changing the frequency f of the control signal V ₁ ~V _4, to weak current mode with greater overlap ratio. As a result, it is possible to limit the increase in the load current, reduce the stress of the switching element, and reduce the distortion of the waveform,
Noise can also be reduced.

Next, FIG. 12 is an explanatory diagram of the operation of the sixth embodiment of the present invention, showing the transition of the state of the circuit operation. The main circuit configuration of the present embodiment is the same as that of the conventional example of FIG. In the lamp startable region, from the state A in which the overlap ratio is reduced to dimming the discharge lamp, the load impedance changes suddenly at the end of the discharge lamp life and the load current increases,
When an abnormality is detected, the control signal V goes up to the state C in the no-load region.
With varying the frequency f of ₁ ~V _4, it continues to increase the overlap ratio gradually limit the increase in the load current by the power supply circuit to the load circuit to reduce the time to be connected,
Finally, the voltage is linearly changed to a weak current mode in which the overlap ratio of the circuit is 100%. As a result, an increase in load current can be limited, and the stress on the switching element can be reduced. In addition, waveform distortion is reduced, and noise can be reduced. Further, according to this embodiment, the circuit can be shifted to the weak current mode in the shortest time.

FIG. 13 is a diagram for explaining the operation of the seventh embodiment of the present invention, showing the transition of the state of the circuit operation. The main circuit configuration of the present embodiment is the same as that of the conventional example of FIG. In order to reduce the output of the discharge lamp, after lighting, the operating frequency is increased, and from the state B operating in the lamp preheatable area,
Load impedance changes suddenly due to the end of discharge lamp life, etc.
When the load current increases and an abnormality is detected, the overlap rate is reduced, and the circuit state is changed to the state C in the no-load area,
Thereafter, to change the operating frequency f of the control signal V ₁ ~V _4. As a result, an increase in load current can be limited by reducing the time during which the power supply circuit is connected to the load circuit, and the stress on the switching element can be reduced. In addition, waveform distortion is reduced, and noise can be reduced. Then, when the load current becomes sufficiently small, the overlap ratio is maximized to set the weak current mode.

Next, FIG. 14 shows the operation of the eighth embodiment of the present invention.
FIG. The main circuit configuration of the present embodiment is different from the conventional example of FIG.
Similarly, each switching element S₁~ S_FourIs the control times
Control signals shown in FIGS. 14A to 14D supplied from the road
V₁~ V_FourIs controlled by Below, specific circuit operation
The work will be described. End of life of discharge lamp during lamp operation
When the load impedance changes suddenly and increases,
Detects abnormalities in load current as load current increases
And time t₀~ T_ThreeThe diagonally located switches are
Increase the on-duty of one of the switching elements and the other
And the switching elements connected in series
At point A and point B
The voltage Vab of FIG. 14 becomes as shown in FIG.
The time when the circuit is connected to the power supply circuit is reduced, and the load current Iz is reduced.
You can limit the increase. And time t _FourMore control signal V₁
~ V_FourThe operating frequency of each
Thus, even if the load current changes sharply,
The time the circuit is connected to the power circuit is reduced,
Limit the increase and reduce the stress on the switching element.
You. In addition, waveform distortion can be reduced and noise can be reduced.
You. Then, when the load current becomes sufficiently small, the overlap ratio
Is set to the maximum and the weak current mode is set.

[0025]

According to the present invention, there is provided a discharge lamp lighting device for driving a load circuit comprising an LC series resonance circuit and a discharge lamp by a full-bridge inverter circuit in which the operating frequency and operating phase of a switching element are variable. When an abnormality such as overvoltage or overcurrent occurs during lighting due to the end of the life of the discharge lamp or the like, the first control means for changing the operation phase is given priority over the second control means for changing the operation frequency to output. It is equipped with an abnormal time protection means for controlling in the limiting direction, so that even if the load current suddenly increases due to a sudden change in the load impedance, the time during which the load circuit is connected to the power supply circuit is shortened, so that the load current is reduced. Limit the increase of the switching element, reduce the stress on the switching element, and reduce the distortion of the waveform, thus reducing the noise. A.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to the present invention.

FIG. 2 is an operation waveform diagram of a conventional example.

FIG. 3 is an operation waveform diagram of the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a transition of a circuit state according to the first embodiment of the present invention.

FIG. 5 is an operation waveform diagram of the second embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a transition of a circuit state according to a second embodiment of the present invention.

FIG. 7 is an operation waveform diagram of the third embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a transition of a circuit state according to a third embodiment of the present invention.

FIG. 9 is an operation waveform diagram of the fourth embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a transition of a circuit state according to a fourth embodiment of the present invention.

FIG. 11 is an explanatory diagram showing a transition of a circuit state according to a fifth embodiment of the present invention.

FIG. 12 is an explanatory diagram showing a transition of a circuit state according to a sixth embodiment of the present invention.

FIG. 13 is an explanatory diagram showing a transition of a circuit state according to a seventh embodiment of the present invention.

FIG. 14 is an operation waveform diagram of the eighth embodiment of the present invention.

[Explanation of symbols]

S _{1 to} S ₄ Switching element L Inductor C Capacitor E AC power supply D Rectifier circuit 1 Control circuit 2 Discharge lamp

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05B 41/24 H02M 7/48 H02M 7/5387

Claims (9)

(57) [Claims] 1. A power supply connected in parallel to a DC power supply and turned on simultaneously.
The first switching element that operates on and off without
A first series circuit with two switching elements, and a DC power supply
Are connected in parallel and turn on and off without turning on at the same time
Between the third switching element and the fourth switching element
A second series circuit and a switch of the first and second series circuits;
At least an inductor connected between the connection points of the switching elements.
Consisting of a discharge lamp and a series resonant circuit of
A load circuit and a switch on the high voltage side of the first series circuit
Switching element and a switching element on the low voltage side of the second series circuit.
And on and off simultaneously with the same switching cycle,
A low-voltage-side switching element of the first series circuit;
The switching element on the high voltage side of the second series circuit is substantially the same
Controlled so that they can be turned on and off almost simultaneously in the switching cycle.
And a control circuit for controlling the discharge lamp.
The control circuit switches on and off almost simultaneously.
The on / off operation of the elements is performed almost simultaneously.
From the same phase, which is the timing of
First control means for continuously changing in the range of
A second control means for changing the wave number, and
The first control means is given priority over the second control means.
Control to limit the current supplied to the load circuit
A discharge lamp lighting device, comprising: 2. An abnormality protection means, when an abnormality occurs, changing an operation frequency while changing an operation phase while fixing an operation frequency to avoid an abnormal state, and then shifting to a weak oscillation mode. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is a means. 3. An abnormal time protection means, when an abnormality occurs, changing an operation phase while fixing an operation frequency to avoid an abnormal state, and then shifting to a weak oscillation mode. 2. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is a means for changing both of them. 4. An abnormality protection means, when an abnormality occurs, changing an operation phase while keeping an operation frequency fixed to avoid an abnormal state, and then changing the operation frequency to a maximum frequency. 3. A means for changing an operation phase so as to shift to a mode.
The discharge lamp lighting device as described in the above. 5. The abnormality protection means is means for, when an abnormality occurs, changing both an operation frequency and an operation phase so as to avoid an abnormal state, and then shifting to a weak oscillation mode. The discharge lamp lighting device according to claim 1, wherein 6. The abnormal time protection means, when an abnormality occurs, changes both the operation frequency and the operation phase to avoid an abnormal state, and then shifts the operation frequency and the operation phase to a weak oscillation mode. 6. The discharge lamp lighting device according to claim 5, wherein the discharge lamp lighting device changes both of them. 7. The abnormality protection means, when an abnormality occurs, changes both the operation frequency and the operation phase to avoid an abnormal state, and then changes the operation phase to shift to a weak oscillation mode. The discharge lamp lighting device according to claim 5, wherein 8. The abnormality protection means, when performing an dimming operation by changing an operation phase, when an abnormality occurs, changes an operation frequency to avoid an abnormal state, and then sets a weak oscillation mode. 2. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is a means for shifting to. 9. An abnormal state protection means, when an abnormality occurs, changes an on-time of at least two sets of diagonally arranged switching elements to avoid an abnormal state, and then shifts to a weak oscillation mode. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is a means.